Filtering assembly and method including removal of impurities from a backwash fluid

ABSTRACT

An assembly for automatically and continuously purifying a polluted fluid P includes a main separator  1 , a secondary separator  2  having a centrifuge  21  and filter  22  therein, and a backwashing device  11 . In operation, the backwashing device returns a fraction of purified fluid E 1  to backwash the main separator. The resulting backwashing fluid F is then delivered to the secondary separator via a multi-port valve V where the backwashing fluid is centrifuged and/or filtered to remove impurities therefrom.

The present invention relates to an assembly for automatically purifyinga polluted fluid, and to a method of implementing said assembly.

The invention relates more particularly to treating oils and gas oilsfor internal combustion engines.

Patent FR 2 725 917 describes a fluid treatment assembly comprising amain separator provided with a backwashing device fed with a fraction ofthe purified fluid, and a secondary separator fed via the outlet duct ofsaid backwashing device with said fraction as charged with impurities.

Unfortunately, the secondary separator is made up of only one centrifugewhose treatment capacity is constant. The capacity is set once and forall by design to accommodate the mean flow rate of the fraction of fluidthat is charged with impurities to be treated and that is delivered fromthe outlet duct of the backwashing device.

That flow rate is itself dependent on the total flow rate of pollutedfluid coming from the motor.

Unfortunately, for a given engine, the polluted fluid flow rate can varyto a considerable extent, in particular as a function of the load on theengine, and it can exceed the predicted values.

Under such conditions, it is sometimes not possible to treat all of theflow rate of charged fluid resulting from backwashing the mainseparator.

A non-negligible fraction of highly-polluted fluid then returns to thetank, which can ultimately cause the fluid circuits of the engine tobecome clogged, giving rise to mechanical or hydraulic breakdowns.

In addition, the centrifuge can separate out only those impurities whichare of a determined density that corresponds in general to precisevalues for the pressure and rotation speed parameters.

Thus, impurities that are of density different from the reference valueare not always separated out.

When the spectrum of the impurities becomes relatively wide, theeffectiveness of the secondary separator is thus significantly reduced.

That also results in problems of clogging and of risks of premature wearor breakdowns.

An object of the present invention is to solve the above-mentionedtechnical problems satisfactorily by adjusting the capacity and theselectivity of the secondary separator to match respectively the flowrates to be treated and the density of the impurities.

This object is achieved by means of an assembly for automatically andcontinuously purifying a polluted fluid, said assembly comprising a mainseparator provided with a backwashing device fed with a fraction of thepurified fluid, and a secondary separator fed via the outlet duct ofsaid backwashing device with said fraction of fluid as charged withimpurities;

said assembly being characterized in that said secondary separatorcomprises a combination of a centrifuge device and of a filter devicewhose capacity and selectivity can be varied as a function firstly ofthe flow rate of said fraction of fluid charged with impurities andsecondly of the range of densities of said impurities.

According to an advantageous characteristic, said centrifuge device andsaid filter device are mounted in parallel on the outlet duct of thebackwashing device.

In a first embodiment, said centrifuge device comprises at least onecentrifuge and preferably two centrifuges in parallel.

In another embodiment, said filter device comprises at least one filterhaving filtering walls.

According to another characteristic, the outlet duct of the backwashingdevice is equipped with a multi-port valve making it possible to isolateat least a portion of the centrifuge device and/or of the filter device.

According to yet another characteristic, said secondary separator andsaid main separator are enclosed inside a common casing.

In a particular embodiment, the outlet duct of the backwashing devicehas a rectilinear upstream segment which extends coaxially with thelongitudinal axis of the main separator and which splits into twodownstream branches that diverge or that extend in opposite directions,each of which feeds a respective portion of the secondary separator.

In a variant embodiment, said secondary separator is disposedtransversely to the main separator.

In another variant, said secondary separator and said main separator aredisposed side-by-side.

The invention also provides a method of automatically and continuouslypurifying a polluted fluid, said method comprising retaining impuritiesin a main separator, backwashing the main separator with a fraction ofpurified fluid, and entraining said fraction as charged with impuritiesto a secondary separator where the impurities are extracted from saidfraction;

said method being characterized in that, in the secondary separator,said fraction charged with impurities is centrifuged and filtered, andin that the capacity and the selectivity of the secondary separator areadjusted as a function respectively of the flow rate of said fractioncharged with impurities, and of the density of said impurities.

According to a characteristic of the method, the capacity and theselectivity of the secondary separator are adjusted automatically byfeeding all or a portion of it or by isolating all or a portion of it.

The purification assembly and the method of the invention make itpossible to obtain highly-effective separation of the impurities with awide density spectrum and regardless of the flow rate of the pollutedfluid to be treated.

Regulating and adapting operation of the secondary separator to matchthe characteristics of the polluted fluid to be purified is performedautomatically. By combining a filter with a centrifuge inside thesecondary separator, it is possible to guarantee a high level of fluidclarification.

In addition, all of the components of the purification assembly areenclosed in a common casing in an ergonomic layout offering maximumcompactness.

The invention will be better understood on reading the followingdescription with reference to the accompanying drawings, in which:

FIG. 1 is a section view of a first embodiment of the purificationassembly of the invention;

FIG. 2 is a section view of a second embodiment of the purificationassembly of the invention; and

FIG. 3 is a fragmentary section view of a variant embodiment of thesecondary separator of the invention.

The treatment assembly shown in the figures is designed forautomatically and continuously purifying a polluted fluid P (such as alubricant, oil, etc.) coming, for example, from an internal combustionengine. Once the impurities with which the fluid becomes charged whileit is being used have been removed from it, it must be recovered andoptionally recycled in the form of a purified fluid.

To this end, the purification assembly comprises a main separator 1enclosed in a casing C, and made up, for example, of a series of filterelements 10 in the form of a stack.

In this example, the filter elements 10 are in the shape of disks, bothfaces 10 a, 10 b of each disk being provided with screens.

The main separator 1 is provided with a backwashing device 11 forbackwashing the filter elements 10. The backwashing device 11 performsbackwashing with a fraction of the purified fluid E₁, thereby enablingthe filter elements to be unclogged, and the impurities that wereretained by the filter elements to be entrained in a fraction F of saidfluid.

The purification assembly further comprises a secondary separator 2 fedvia the outlet duct 12 of the backwashing device 11 with the fraction Fof fluid charged with impurities.

The main separator 1 and the secondary separator 2 are enclosed in acommon casing C.

The purpose of the secondary separator is to extract as large a quantityas possible of the impurities present in the fraction F so as to delivera minority fraction E₂ of purified fluid, suitable for being returned tothe fluid tank or for being recycled directly in the engine togetherwith the majority fraction E₁ of fluid purified by the main separator 1.

However, the flow rate of polluted fluid P to be treated in the mainseparator 1 can vary. Such variation causes fluctuations in the flowrate of the fraction F. When such fluctuations are constituted by asignificant increase in the flow rate of the fraction F, the secondaryseparator must be capable of treating the entire flow rate with the sameeffectiveness as it does when it treats lower flow rates.

Regardless of the flow rate to be treated, the fraction E₂ of fluid musthave a predetermined degree of purity that is in the vicinity of thedegree of purity of the fraction E₁.

Similarly, the characteristics (size, density, etc.) of the impuritiesto be separated out can vary over relatively wide ranges, and thetreatment implemented in the secondary separator must result in thelargest possible number of impurities being separated out.

To these ends, and in the invention, provision is made for the secondaryseparator to comprise a centrifuge device 21 and a filter device 22whose capacity and selectivity can be varied as a function firstly ofthe flow rate of the fraction F of fluid charged with impurities, andsecondly of the range of densities of said impurities.

In the embodiment shown in FIG. 1, the main separator 1 and thesecondary separator 2 are mounted side-by-side. The centrifuge device 21and the filter device 22 are mounted in parallel on the outlet duct 12of the backwashing device 11.

Thus a portion F₂ of the flow fees the centrifuge device 21 while anadditional portion F feeds the filter device 22.

Preferably, the filter device 22 comprises at least one filter havingfiltering walls or selective screens, while the centrifuge device 21comprises at least one centrifuge, and preferably two centrifuges inparallel (second centrifuge not illustrated). The capacities and thespeeds of rotation of the centrifuges may optionally differ from onecentrifuge to the other, as may the selectivity (or pore size) of thevarious filters, so as to adjust the treatment as a function of therespective characteristics of the flow F and of the impurities to betreated.

After being filtered, the flow F₁ flows into a fist chamber 23surrounding the filter and communicating with a second chamber 24enclosing the centrifuges.

The chambers 23, 24 are delimited outside the frame B of the mainseparator 1 by removable covers 230, 240 making it possible formaintenance to be performed on the filter device 22 and on thecentrifuge device 21.

The centrifuges are rotated by means of the reaction effect of thepurified fluid which flows out via opposite nozzles 21 a, 21 b of thecentrifuge 21, relative to the fluid contained in the chamber 24.

In the second chamber 24, the purified flows F₁ and ₂ mix together toform a fraction E₂ which is removed from the casing C via a duct 20.

Preferably, as shown in FIG. 3, the outlet duct 12 of the backwashingdevice is equipped with a multi-port valve V making it possible to openor to isolate all or at least a portion of the secondary separator, inparticular when the flow rate of the fraction F varies.

Th valve V is controlled automatically by an actuator (A) coupled to aflow meter (FM) mounted on the duct 12, or further upstream, so as toadjust automatically the treatment capacity and the selectivity of thesecondary separator.

The value V is connected to the outlet duct 12 of the backwashingdevice, and it is disposed in the center of the secondary separator 2between the centrifuge chamber 24 and the filter chamber 23.

In the embodiment shown in FIG. 2, the secondary separator 2 is disposedtransversely to the main separator 1.

In which case, the outlet duct 12 of the backwashing device 11 has arectilinear upstream segment 12 a which extends coaxially to thelongitudinal axis of the main separator 1 and which splits into twodownstream branches 12 b, 12 c diverging or extending in oppositedirections at 180° to each other, each branch feeding a respectiveportion of the secondary separator 2.

In this example, the branch 12 b extends towards the centrifuge device21, while the branch 12 c leads to the filter device 22.

What is claimed is:
 1. An assembly for automatically and continuouslypurifying a polluted fluid (P), said assembly comprising: a. a mainseparator (1) provided with a backwashing device (11) for a separatorsystem (10), the backwashing device (11) receiving, following thepassage of a fraction of purified fluid (E1) through the separatorsystem (10), a fraction of backwashing fluid (F) charged with impuritiesfrom the separator system (10); b. a secondary separator (2) fed via anoutlet duct (12) of said backwashing device (11) with said fraction ofbackwashing fluid (F) charged with impurities, said secondary separator(2) comprising in combination: i. a centrifuge device (21) including atleast one centrifuge, and ii. a filter device (22) including at leastone filter having filtering walls; and c. a multi-port valve disposed inthe outlet duct (12) of the backwashing device, said multi-port valveadapted to allow each of the filter and centrifuge device to receive allor a portion of the backwashing fluid F from the outlet duct (12).
 2. Anassembly according to claim 1, characterized in that said centrifugedevice (21) and said filter device (22) are mounted in parallel on theoutlet duct (12) of the backwashing device (11).
 3. An assemblyaccording to claim 2, characterized in that said centrifuge device (21)comprises two centrifuges in parallel.
 4. An assembly according to claim3, characterized in that said secondary separator (2) and said mainseparator (1) are enclosed inside a common casing (c).
 5. An assemblyaccording to claim 3, characterized in that the outlet duct (12) of thebackwashing device (11) has a rectilinear upstream segment (12 a) whichextends coaxially with the longitudinal axis of the main separator (1)and which splits into two downstream branches (12 b, 12 c) that diverge,respectively feeding the centrifuge device and the filter device.
 6. Anassembly according to claim 2, characterized in that the multi-portvalve is controlled automatically by an actuator coupled to a flow metermounted on the outlet duct (12).
 7. An assembly according to claim 2,characterized in that said secondary separator (2) and said mainseparator (1) are enclosed inside a common casing (c).
 8. An assemblyaccording to claim 7, characterized in that the outlet duct (12) of thebackwashing device (11) has a rectilinear upstream segment (12 a) whichextends coaxially with the longitudinal axis of the main separator (1)and which splits into two downstream branches (12 b, 12 c) that diverge,respectively feeding the centrifuge device and the filter device.
 9. Anassembly according to claim 2, characterized in that the outlet duct(12) of the backwashing device (11) has a rectilinear upstream segment(12 a) which extends coaxially with the longitudinal axis of the mainseparator (1) and which splits into two downstream branches (12 b, 12 c)that diverge, respectively feeding the centrifuge device and the filterdevice.
 10. An assembly according to claim 1, characterized in that saidcentrifuge device (21) comprises two centrifuges in parallel.
 11. Anassembly according to claim 10, characterized in that the multi-portvalve is controlled automatically by an actuator coupled to a flow metermounted on the outlet duct (12).
 12. An assembly according to claim 10,characterized in that said secondary separator (2) and said mainseparator (1) are enclosed inside a common casing (c).
 13. An assemblyaccording to claim 12, characterized in that the outlet duct (12) of thebackwashing device (11) has a rectilinear upstream segment (12 a) whichextends coaxially with the longitudinal axis of the main separator (1)and which splits into two downstream branches (12 b, 12 c) that diverge,respectively feeding the centrifuge device and the filter device.
 14. Anassembly according to claim 10, characterized in that the outlet duct(12) of the backwashing device (11) has a rectilinear upstream segment(12 a) which extends coaxially with the longitudinal axis of the mainseparator (1) and which splits into two downstream branches (12 b, 12 c)that diverge, respectively feeding the centrifuge device and the filterdevice.
 15. An assembly according to claim 1, characterized in that saidsecondary separator (2) and said main separator (1) are enclosed insidea common casing (c).
 16. An assembly according to claim 15,characterized in that the multi-port valve is controlled automaticallyby an actuator coupled to a flow meter mounted on the outlet duct (12).17. An assembly according to claim 15, characterized in that the outletduct (12) of the backwashing device (11) has a rectilinear upstreamsegment (12 a) which extends coaxially with the longitudinal axis of themain separator (1) and which splits into two downstream branches (12 b,12 c) that diverge, respectively feeding the centrifuge device and thefilter device.
 18. An assembly according to claim 1, characterized inthat the outlet duct (12) of the backwashing device (11) has arectilinear upstream segment (12 a) which extends coaxially with thelongitudinal axis of the main separator (1) and which splits into twodownstream branches (12 b, 12 c) that diverge, respectively feeding thecentrifuge device and the filter device.
 19. An assembly according toclaim 18, characterized in that the two downstream branches (12 b, 12 c)of the centrifuge and filter devices are perpendicular to the upstreamsegment (12 a) of the outlet duct (12) of the backwashing device, and inthat the two branches (12 b, 12 c) extend in opposite directions at 180°to each other.
 20. An assembly according to claim 18, characterized inthat the multi-port valve is controlled automatically by an actuatorcoupled to a flow meter mounted on the outlet duct (12).
 21. An assemblyaccording to claim 1, characterized in that the multi-port valve iscontrolled automatically by an actuator coupled to a flow meter mountedon the outlet duct (12).
 22. A method of automatically and continuouslypurifying a polluted fluid (P), said method comprising the steps of: a.retaining impurities from the polluted fluid (P) in a main separator(1); b. backwashing the main separator (1) with a fraction of purifiedfluid (El) to produce a fraction of backwashing fluid (F) charged withsaid impurities; c. delivering said fraction of backwashing fluid (F) toa secondary separator (2) comprising a centrifuge and a filter havingfiltering walls, wherein the amount of backwashing fluid delivered toeach of said centrifuge and said filter is selectively controlled; andd. extracting said impurities from said fraction of backwashing fluid(F) by centrifuging and filtering said fraction of backwashing fluid (F)in said secondary separator (2).